Method of using an apparatus to automatically control sudden changes in volume

ABSTRACT

A method includes comparing a magnitude value of an audio signal in a fixed unit section with a target volume level, measuring audio gain in each fixed unit section using specific functions which are each determined to be different according to a ratio of the target volume level to the audio signal magnitude, and providing the measured audio gain to the audio signal in the fixed unit section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(a) from KoreanPatent Application No. 10-2008-0009005, filed on Jan. 29, 2008, in theKorean Intellectual Property Office, the disclosure of which isincorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates to an audio reproductionsystem, and more particularly, to a method and apparatus toautomatically control audio volume that suddenly changes betweenchannels or scenes.

2. Description of the Related Art

Currently, due to a rapid development of communication and broadcastingtechnologies and combining of communication and broadcasting fields, aservice for conveniently watching digital broadcasting while moving isprovided.

In general, audio and video (AV) reproduction devices such as digitaltelevisions (DTVs) or home theaters allow viewers to watch TV or videoof a personal video recorder (PVR) by connecting to various externaldevices and selecting various types of signals and broadcast channelsfor watching terrestrial analog broadcasting, satellite broadcasting,and cable broadcasting.

In conventional DTVs or home theaters, when a user changes a channel ora scene is changed, an audio volume level suddenly changes and thus theuser feels uncomfortable.

For example, a user individually changes channels of DTVs to identify acondition of a screen. The DTVs automatically and sequentially searchfor broadcast channels of received frequency bands.

However, while changing channels, a user feels that volume levels ofeach broadcast channel are slightly different which occurs due to areceive sensitivity of each broadcast channel. Accordingly, such avolume change due to changing channels should be corrected.

Thus, in conventional AV reproduction devices, a method of controllingaudio volume using a linear curve is used to correct a volume changeoccurring due to the changing of channels or scenes.

FIGS. 1A and 1B are graphs illustrating a relationship betweenmagnitudes of input audio signals and output audio signals used in theconventional method of controlling audio volume.

Referring to FIG. 1A, the conventional method of controlling audiovolume defines a volume controlling section as three sections such as aboost section 110, a no modification section 120, and a cut section 130.

For example, when a volume of the audio signal is above an optimum level(cut section 130), a gain of the audio signal decreases. When the volumeof the audio signal is at an optimum level (no modification section120), the gain of the audio signal is maintained. When the volume of theaudio signal is below an optimum level (boost section 110), the gain ofthe audio signal increases.

However, as illustrated in FIG. 1B, the volume cannot be controlled in acenter portion 150 of the no modification section 120 and sounddeterioration occurs due to discontinuous control in a first boundaryportion 140 of the boost section 110 and the no modification section 120and a second boundary portion 160 of the cut section 130 and the nomodification section 120.

SUMMARY OF THE INVENTION

The present general inventive concept provides a method and apparatus tocontrol audio volume, to automatically normalize a volume that suddenlychanges between channels or scenes, by obtaining a gain of an audiosignal that is appropriate for each frame using exponential functioninput/output curves and active section allocation.

Additional aspects and utilities of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the general inventive concept.

The foregoing and/or other aspects and utilities of the generalinventive concept may be achieved by providing a method of automaticallycontrolling audio volume, the method including comparing a magnitudevalue of an audio signal in a fixed unit section with a target volumelevel, measuring an audio gain in each fixed unit section using specificfunctions which are each determined to be different according to a ratioof the target volume level to the audio signal magnitude, and providingthe measured audio gain to the audio signal in the fixed unit section.

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing an apparatus toautomatically control audio volume, the apparatus including a framepower calculating unit to calculate a power value of an input audiosignal for each fixed section unit, a volume controller to compare amagnitude of an audio signal calculated in the frame power calculatingunit with a determined target volume level and to measure an audio gainusing specific functions which are each determined to be differentaccording to a ratio of the magnitude value of the audio signal to thetarget volume level, and an output buffer unit to output an audio signalto which the audio gain measured in the volume controller is applied.

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing an audioreproduction system including an audio volume controller to compare amagnitude of an audio signal in a fixed time unit with a target volumelevel and to control audio volume by an audio gain using exponentialfunctions that are each different according to a ratio of the magnitudeof the audio signal to the target volume level, and an amplifier unit toamplify the audio signal output from the audio volume controller to apredetermined magnitude.

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing an apparatus tocontrol audio volume, the apparatus including a volume controller toapply predetermined exponential functions to obtain a respective gaincorresponding to each of a plurality of fixed unit sections, wherein thevolume controller automatically normalizes a volume to prevent thevolume from sudden changes between channels or scenes.

The volume controller may compare a magnitude value of an audio signaland a target volume level such that the respective gain of the audiosignal is changed by controlling an exponential value of the respectiveexponential function based on the comparison.

The respective gain of the audio signal may be decreased when themagnitude value of the audio signal is larger than the target volume andthe respective gain of the audio signal may be when the magnitude valueof the audio signal is smaller than the target volume.

The volume controller may control the volume of an audio signalaccording to a boost section, a no modification section, and a cutsection, and controls the volume of the audio signal according to thegain corresponding to a boundary between the no-modification section andat least one of the boost section and the cut section.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and utilities of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompanying drawings of which:

FIGS. 1A and 1B are graphs illustrating a relationship betweenmagnitudes of input audio signals and output audio signals used in aconventional method of controlling audio volume;

FIG. 2 is a block diagram illustrating an audio reproduction systemaccording to an embodiment of the present general inventive concept;

FIG. 3 is a block diagram illustrating an audio volume controller ofFIG. 2 in more detail;

FIG. 4 is a flowchart illustrating a method of automatically controllingaudio volume according to an embodiment of the present general inventiveconcept;

FIG. 5 is a graph illustrating an input/output function indicating arelationship between magnitudes of input audio signals and output audiosignals according to an embodiment of the present general inventiveconcept; and

FIGS. 6A through 6C respectively illustrate a waveform of an originalsignal, a waveform of a signal planarized by using a conventionaltechnology, and a waveform of a signal planarized by using a technologyaccording to an embodiment of the present general inventive concept withrespect to a sudden volume change between channels/scenes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to the likeelements throughout. The embodiments are described below in order toexplain the present general inventive concept by referring to thefigures.

FIG. 2 is a block diagram illustrating an audio reproduction systemaccording to an embodiment of the present general inventive concept.

The audio reproduction system includes a key input unit 210, a storageunit 220, an audio volume controller 230, an amplifier unit 240, and aspeaker unit 250.

The key input unit 210 is formed of a keypad or a touch screen andincludes a plurality of number/letter input keys to select variousfunction operations and function keys to interface with a user.

The storage unit 220 is formed of a Read Only Memory (ROM) and/or avoice memory to store various programs and data, such as a target volumelevel determined by a user and a look-up table.

The audio volume controller 230 compares a magnitude of an audio signalin a time unit (for example, a frame, a predetermined time unit or afixed time unit) with the target volume level and controls an audiovolume using exponential functions that are each different according toa ratio of the target volume level to the audio signal magnitude.

The amplifier unit 240 amplifies the audio signal output from the audiovolume controller 230 so as to increase the magnitude of the signal thatis to be reproduced by a speaker.

The speaker unit 250 reproduces the audio signal amplified by theamplifier unit 240 to a sound in an audio frequency band.

FIG. 3 is a block diagram illustrating the audio volume controller 230of FIG. 2 in more detail.

The audio volume controller 230 includes an input buffer unit 310, aframe power measuring unit 320, a target volume storage unit 330, alook-up table unit 350, a volume controller 340, and an output bufferunit 360.

The input buffer unit 310 buffers an input audio signal in a pulse codemodulation (PCM) form.

The frame power measuring unit 320 measures a power value (or amagnitude value) of the audio signal stored in the input buffer unit 310for each fixed section. For example, the frame power measuring unit 320divides the input audio signal into frame units, applies a windowfunction to each frame, and measures the power value of the audio signalcorresponding to a root mean square (RMS) for each frame unit. Here, awindowing method generally uses a Hamming window and a Hanning window.

The target volume storage unit 330 stores the target volume levelarbitrarily set by a user.

The volume controller 340 compares the power value of the audio signalmeasured in the frame power measuring unit 320 and the target volumelevel stored in the target volume storage unit 330 and appliesexponential functions previously determined according to a ratio of thetarget volume level to the audio signal magnitude to the input audiovolume, so as to obtain an audio gain for each fixed unit section.

Here, the volume controller 340 uses the look-up table unit 350 or anexponential operation performed by a processor to obtain the gain.

The look-up table unit 350 stores the gains of the audio signal that areeach different and are optimally determined according to a ratio of thepower value of the audio signal to the target volume level, in a look-uptable form.

The output buffer unit 360 outputs the audio signal in which the audiogain generated from the volume controller 340 is applied to the audiosignal output from the input buffer unit 310.

FIG. 4 is a flowchart illustrating a method of automatically controllingaudio volume according to an embodiment of the present general inventiveconcept.

Firstly, the audio signal in a PCM form is input in operation 410.

Then, the input audio signal is divided into the frame units and thepower value of the audio signal corresponding to the RMS value ismeasured for each frame unit in operation 420.

In operation 430, the power value of the audio signal is compared withthe target volume level arbitrarily determined by the user.

In operation 440, the ratio of the power value of the input audio signalto the target volume level is measured.

Then, the exponential functions differently determined according to theratios of the magnitude of the audio signal, compared with the targetvolume level are applied to the ratio of the magnitude of the inputaudio signal to the target volume and the audio gain for each fixed unitsection is obtained in operation 450.

Here, the ratios of the magnitude of the audio signal to the targetvolume level are classified into a plurality of ranges and theexponential function included in the corresponding range is applied tothe ratio of the magnitude of the input audio signal to the targetvolume.

For example, assuming that the magnitude value of the input audio signalis x, the target volume is c, and the ratio x/c of the magnitude of theinput audio signal to the target volume is classified into five cases asfollows.

(1) x/c<0.01 (when x/c is below 1%)

(2) 0.01<x/c<0.1 (when x/c is between 1% and 10%)

(3) 0.1<x/c<2 (when x/c is between 10%-200%)

(4) 2<x/c<10 (when x/c is between 200%-1000%)

(5) 10<x/c (when x/c is above 1000%)

Here, people recognize the sound by a log scale so that the gain of theaudio signal can be realized by the exponential function.

Accordingly, the audio gains for each frame are obtained using the ratioof the power value of the audio signal to the target volume, in whichthe exponential functions that are different according to the magnitudevalue of the audio signal, compared with the target volume. Eachdifferent exponential function having continuous characteristicsaccording to the ratio of the magnitude value of the audio signal to thetarget volume are set in each case.

For example, when (1) x/c<0.01, the gain g1 is (x/c)^(0.6), when (2)0.01<x/c<0.1, the gain g2 is (x/c)^(0.8), when 3) 0.1<x/c<2, the gain g3is (x/c)^(1.2), when (4) 2<x/c<10, the gain g4 is (x/c)^(1.4), and when(5) 10<x/c, the gain g5 is (x/c)^(1.8).

That is, when the magnitude value of the input audio signal is largerthan the target volume, the gain of the audio signal should be decreasedby controlling the exponential value of the exponential function. Whenthe magnitude value of the input audio signal is smaller than the targetvolume, the gain of the audio signal should be increased by controllingthe exponential value of the exponential function.

Here, a method of extracting the gain of the audio signal may includedirectly measuring the exponential function performed by the processorand using the look-up table in which the gain of the audio signalpreviously determined is stored. Here, the look-up table stores thegains of the audio signal to which the exponential functions that areeach different according to the ratio of the magnitude value of theaudio signal to the target volume are applied.

Then, the gains of the audio signal obtained by each fixed unit sectionare applied to the audio signals input by each fixed unit section inoperation 460. For example, when the exponential value is α, the outputsignal (y) may be represented by (x/c)^(α)×x.

FIG. 5 is a graph illustrating an input/output function indicating arelationship between magnitudes of input audio signals and output audiosignals according to an embodiment of the present general inventiveconcept.

Referring to FIG. 5, people recognize sound according to a log scale sothat the gain of the audio signal can be realized by the exponentialfunction.

Accordingly, the ratio of the magnitude value of the audio signal to thetarget volume is divided into, for example, five cases (1) to (5), andeach different exponential function in which an auditory characteristicis reflected is applied to each case.

In addition, continuous exponential functions are applied to each casein order for discontinuous volume not to occur.

FIGS. 6A through 6C illustrate a signal planarized from an originalsignal by using a conventional technology and a signal planarized froman original signal by using a technology according to an embodiment ofthe present general inventive concept with respect to a sudden volumechange between channels/scenes.

FIG. 6A illustrates a waveform of an original signal having a suddenvolume change between channels/scenes.

FIG. 6B illustrates a waveform of a signal planarized using aconventional technology with respect to a sudden volume change betweenchannels/scenes.

Referring to FIG. 6B, a planarization degree of signals 610 and 620having a sudden volume change between channels/scenes is weak.

FIG. 6C illustrates a waveform of a signal planarized using a technologyaccording to an embodiment of the present general inventive concept withrespect to a sudden volume change between channels/scenes.

Referring to FIG. 6C, the planarization degree of signals 630 and 640having a sudden volume change between channels/scenes is high.

As described above, according to various embodiment of the presentgeneral inventive concept, the gain of an audio signal that isappropriate for each frame is obtained using an exponential functioninput/output curve in which an auditory characteristic is reflected sothat inconveniences occurring due to a volume difference between thechannels/scenes, a signal level difference in the audio signals betweenmultimedia applications, the volume difference between various mediafiles according to an encoded signal level difference can be resolved.Thus, the method and apparatus to automatically control audio volumeaccording to various embodiments of the present general inventiveconcept can be efficiently applied to DTVs, home theater, MP3reproduction devices, mobile AV devices, and laptop PCs so as toincrease performances thereof.

The present general inventive concept can also be embodied ascomputer-readable codes on a computer-readable recording medium. Thecomputer-readable medium can include a computer-readable recordingmedium and a computer-readable transmission medium. Thecomputer-readable recording medium is any data storage device that canstore data which can be thereafter read by a computer system. Examplesof the computer-readable recording medium include read-only-memory(ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppydisks, and optical data storage devices. The computer-readable recordingmedium can also be distributed over network coupled computer systems sothat the computer-readable code is stored and executed in a distributedfashion. The computer-readable transmission medium can transmit carrierwaves or signals (e.g., wired or wireless data transmission through theInternet). Also, functional programs, codes, and code segments toaccomplish the present general inventive concept can be easily construedby programmers skilled in the art to which the present general inventiveconcept pertains.

While the present general inventive concept has been particularlyillustrated and described with reference to exemplary embodimentsthereof, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present general inventiveconcept as defined by the following claims.

1. A method of automatically controlling audio volume, the methodcomprising: comparing a magnitude value of an audio signal in a fixedunit section with a target volume level; measuring an audio gain in eachfixed unit section using specific functions which are each determined tobe different with regard to a ratio of the target volume level to theaudio signal magnitude; and providing the measured audio gain to theaudio signal in the fixed unit section.
 2. The method of claim 1,wherein measuring the audio gain comprises: classifying the ratio of themagnitude value of the audio signal to the target volume level into aplurality of cases and applying a plurality of functions allocated to acase in which a ratio of the magnitude value of the audio signal to thetarget volume level is included, to the ratio of the magnitude value ofthe audio signal to the target volume level.
 3. The method of claim 2,wherein the plurality of functions are each set differently according tothe ratio of the magnitude value of the audio signal to the targetvolume level.
 4. The method of claim 1, wherein the target volume levelis determined arbitrarily by a user.
 5. The method of claim 1, whereinthe plurality of functions are exponential functions in which anauditory characteristic is reflected.
 6. The method of claim 1, whereinthe measuring of the audio gain comprises: applying an exponentialfunction curve having a continuous characteristic to the ratio of themagnitude value of the audio signal to the target volume level.
 7. Themethod of claim 1, wherein the audio gain in each fixed unit section towhich a specific function is applied according to the ratio of themagnitude value of the audio signal to the target volume level is storedin a look-up table.
 8. The method of claim 1, wherein the audio gain ineach fixed unit section is measured by applying the determinedexponential function to the ratio of the magnitude value of the audiosignal to the target volume level.
 9. A computer-readable recordingmedium having embodied thereon a computer program to execute a method,the method comprising: comparing a magnitude value of an audio signal ina fixed unit section with a target volume level; measuring audio gain ineach fixed unit section using specific functions which are eachdetermined to be different with regard to a ratio of target volume levelto the audio signal magnitude; and providing the measured audio gain tothe audio signal in the fixed unit section.